1. Field of the Invention
The invention relates to an assembly machine comprising a machine frame, a plurality of work stations that are arranged on a circular carrier plate that is secured on the top side of the machine frame, and a rotary dish that is rotationally driven in cycles and arranged concentrically in relation to the carrier plate. The rotary dish protrudes over the circumference of the carrier plate and forms a support surface in the form of a ring for work pieces that surround the carrier plate.
2. The Prior Art
An assembly machine is described in DE-A 43 28, 988, in which the frame of the machine is realized in the form of a welded construction, and there is an electromechanical drive with a stopping-and-stepping gearing that serves as the drive for the rotary dish. The stopping-and-stepping gearing, with the rotary dish mounted on it, forms an independent subassembly. The stopping-and-stepping gearing has to be designed in different ways based on the diameter of the rotary dish and depending on the number of work stations or the stepping distance over which the rotary dish has to travel in one work cycle. Due to the fact that the assembly machine has to be precisely adapted to various applications with respect to the diameter of the rotary dish and the number of work stations present, the manufacture of an assembly machine can be started only after the specifications have been on the application side. In practical life, this frequently results in long delivery times.
It is therefore an object of the invention to provide a basic assembly machine that can be variably adapted to different assembly-tasks with respect to the size of the rotary dish and the stepping distance (or width) of one work cycle without having to make any constructional changes on the machine frame or the drive of the rotary dish.
Based on an assembly machine with the structure described above, the invention comprises a machine frame in the form of a cast part that has a table-like substructure and a top-side console with a ring-shaped mounting surface for receiving a drive for the rotary dish. The drive of the rotary dish is a direct drive that comprises a ring-shaped stator with electrical windings and being secured on the mounting surface, as well as a rotor fitted with permanent magnets. The rotor forms a carrier for the rotary dish and is connected with the dish in a detachable manner. The machine frame form of a cast component of the machine, and the drive of the rotary dish, form one functional subassembly that can be prefabricated.
The invention profits from the fact that the cast component has high dimensional stability, and that the mounting surface for receiving the drive of the rotary dish can be precisely worked. The rotor of the electrical direct drive, which is also referred to as a torque motor, supports the rotary dish on a ring-shaped support surface with a large diameter. Tilting movements of the rotary dish are excluded in this way.
Differently sized rotary dishes can be readily mounted on the support surface without having to fear any impairment with respect to its function. The division of the rotary dish and the speed of the rotational movement are determined by the programming of the torque motor and can be variably adapted to each individual application as required by changing the control software. Furthermore, the rotary dish can be divided in a manner that cannot be accomplished with a mechanical drive for constructional reasons.
The stator of the electrical direct drive may optionally have a segmented structure. A mechanical clamping or braking device may be provided, so that the rotary dish cannot move as work pieces positioned on the rotary dish are being processed in the work stations.
The table-like substructure of the cast component preferably comprises two lateral wings (or side structures) whose bottoms are secured on a base plate. For weight reasons, but also for improving the accessibility, the cast machine component may contain window-like recesses. A work plate for securing additional equipment and feed devices is usefully arranged on the table-like substructure. According to a preferred embodiment of the invention, the carrier plate and the rotary dish are in the form of ring-shaped plates, and drives and control devices are arranged within the table-like substructure for actuating assembly tools in the work stations. Cables leading to the work stations for controlling the assembly tools can be installed through the clear space of the carrier plate and the rotary dish.
According to a preferred embodiment of the invention, the rotor of the torque motor that is employed as the drive for the rotary dish consists of a bearing ring of an antifriction bearing arranged on the mounting surface. This bearing ring is fitted with permanent magnets. The antifriction bearing comprises a bearing ring fixed on the mounting ring, rollers, and a movable bearing ring that forms the rotor, which, as a sub-supplied component, can be manufactured with high precision.
According to a particularly preferred embodiment of the invention, the stator is an outer ring that has electrical windings on its circumferential surface on the inner side. The antifriction bearing ring forming the rotor is a component of an antifriction bearing that is arranged within the outer ring concentrically in relation to the latter. The outer ring may be structured as one single part or from segments.
According to a further development of the invention, the stator has cooling channels that can be accessed from the outside, and a gasket is arranged on the outer ring for sealing a gap between the stator and the rotary dish. With the stator comprising an outer ring, and with additional sealing versus the rotary dish, the antifriction bearing is protected against contamination. This design is also suitable for application in sterile rooms, for example in the field of medical technology. The carrier plate supporting the work stations may rest on the inner ring of the antifriction bearing that is arranged on the mounting surface in a fixed manner, and can be secured on the inner ring. This arrangement has a very simple construction.